Differential sensing circuitry is preferred for determining the binary value stored in the capacitor of each cell. In most such sensing circuit arrangements, one input terminal is arranged to receive a potential level substantially equal to the binary value stored. The other input terminal of the sensing circuitry is arranged with fixed reference potential applied. Depending on the mode of operation desired, the sensing circuitry is arranged to deliver binary output levels proportional to the algebraic differences between the reference potential and the input potential values. A preferred mode is centered about a reference potential that is substantially midway of the binary value levels.